The present invention relates to an improved hand-free system for use on a cellular phone, and more particularly to one which can prevent an automatically-operated antenna of a vehicle's audio stereo system from being unnecessarily actuated in response to incoming signals of a cellular phone. As a cellular phone is receiving incoming signals, a vehicle's audio stereo system in operation is automatically turned off or become mute, and the received voice signals of the cellular phone are amplified and broadcast via speakers of the vehicle's audio stereo system. At the same time, the antenna of the vehicle's audio stereo system remains in its current status without being actuated till the end of the operation of a cellular phone; afterwards, the audio stereo system is automatically started again. Thereby, it not only advances the quality of communication of a cellular phone and driving safety of a vehicle but also make the operation life of an antenna of a vehicle effectively extended by reducing the number of unnecessary extensions and retractions of the antenna in use.
Local civil communication markets are now opened to more and more competitors together with the domestic cellular phone markets in addition. The number of users of cellular phones is increasing in multiple times. Under such a circumstance, consumers expect more functions for a cellular phone and more kinds of peripheral equipment are designed and marketed one after the other for years. Among them hand-free systems are the most prospective products on markets all over the world. However, cellular phones are changing in functions, sizes and outer appearance rapidly to meet different consumers' requirements. Members of a family may have various kinds of cellular phones. So, a hand-free system used in a vehicle for one specific kind of cellular phone is out of date now. The inventor has already worked on a resolution for this problem and come up with a universal hand-free system applied for a patent in his previous invention.
More and more vehicles are equipped with a high level audio stereo system, which generally has an automatically operated antenna extending and retracting according to control signals. A hand-free system operated in combination with such a vehicle's audio stereo system will turn off the audio stereo system when a cellular phone is receiving incoming signals so as to permit voice signals to be transmitted by way of speakers of the vehicle's audio stereo system. If a general audio stereo system is equipped with a mute function, the audio system is set mute in that case, if it is not equipped with such a function, the power source of the audio system is to be controlled. However, most of vehicles' audio stereo systems do not have a mute function, so, the present invention resorts to the control of a power source.
As a result of the audio stereo system being turned off at the moment of the cellular phone receiving incoming signals, an automatic antenna of the vehicle is controlled to retract automatically. The antenna is extended after the operating cellular phone comes to an end with the audio stereo system turned on again. Such a repetition of extending and retracting operations on an antenna can make the operation life thereof shortened easily and also cause damage to the same readily.